This invention relates in general to the fuel efficient control of multiple unit locomotive consists. More particularly, the invention is directed to improvements in the type of control system disclosed in pending application Ser. No. 165,724, filed July 3, 1980 in the name of Rudolph D. Spigarelli, John L. Aker and Fred M. Berry.
As described in the aforementioned application, substantial fuel savings can be achieved in the operation of multiple unit locomotive consists if the diesel electric locomotive engines are controlled such that they operate at either the full power No. 8 setting, the half power No. 5 setting, or the No. 1 throttle setting which is essentially the idle engine position giving minimal power. The desired train speed can normally be maintained with this arrangement, and the consist operates efficiently because what locomotive units are needed are for the most part operated at the fuel efficient No. 8 throttle position. At any given time, one locomotive at the most can be in the No. 5 throttle position.
The control apparatus disclosed in the aforementioned Spigarelli et al application has proven to be highly effective in reducing the fuel consumption of locomotive consists and has been highly satisfactory for the most part. However, it has not been wholly free of problems. Perhaps most notably, it has been found in actual practice that the engineers at times apply the automatic air brake of the locomotive consists while the locomotives are operating under power. This not only wastes fuel but also adds unduly to the wear on the train wheels, brake shoes, and track. The added wear on the wheels and brake shoes alone increases the operating and maintenance costs by significant amounts.
Another problem has been that application of the dynamic brake takes the consist out of the fuel save mode of operation, and the engineer can then control the consist manually. It is generally desirable to provide the engineer with manual throttle control when he returns the consist to power from the dynamic brake mode, since he must apply sufficient power to gradually stretch the train from the "bunched" condition that occurs in the dynamic brake mode. However, since many engineers have resisted the device because it takes away some of their control of the consist, there is a tendency for some engineers to apply the dynamic brake solely for the purpose of gaining manual control. Consequently, the dynamic brake is overused and the fuel saver device is not utilized to full advantage. In addition, it has been possible for the engineer to set the speed of the locomotive consist at an unduly high or low level, thus operating the consist at speeds outside of the accepted range.
The system of the aforementioned patent application also requires a number of relays which must be wired into the circuitry at the proper locations. The need for numerous relays and the attendant wiring adds significantly to the costs and the time required for installation, and the relays also detract somewhat from the reliability of the system.
The present invention is directed toward an improved control device for operating a multiple unit locomotive consist in a fuel efficient manner. In accordance with the invention, the locomotives in a multiple unit consist are controlled in essentially the same manner disclosed in the aforementioned Spigarelli et al patent application. In order to achieve efficiency in a fuel save mode of operation, each locomotive needed to maintain the desired speed is maintained at the fuel efficient No. 8 throttle setting, or at times at the half power No. 5 setting. Any locomotives not needed are placed in the No. 1 throttle position. Extended high horsepower power braking is avoided by automatically dropping all trailing locomotive units to the full power reduction status once the air brakes have been applied for a predetermined time, generally 30-60 seconds. Also eliminated is abuse of the dynamic brake for the purpose of getting control of the consist in the hands of the engineer. When the dynamic brake is released after having been applied for at least 30 seconds, an override period is initiated to give the engineer manual control of the consist for 90 seconds. The 90 second override period provides sufficient time for the engineer to gradually stretch out the train from the bunched condition, while the 30 second period required for initiation of the override period keeps the engineer from applying the dynamic brake for a minimal time just to gain control.
Another important feature of the invention is the provision of minimum and maximum speed setting switches which determine the range of speeds at which the control system operates to cause power reductions (except in the automatic air brake mode). The switches are inaccessible to the crew so that their settings cannot be altered without authorization. If the train speed drops below the minimum setting, the consist gradually reverts to manual control so that the engineer can handle it in the manner required to avoid problems.
An additional feature of significance is the use of solid state components to properly energize and deenergize the governor solenoids of the locomotive engines in accordance with commands that are issued from the control system. The use of solid state controls instead of numerous relays simplifies the installation and reduces the overall costs.
The invention also operates to restrict the dynamic brake loading to a preselected numer of axles, typically a maximum of 24 axles in accordance with normal industry practice. Although conventional practice provides switches in the cabs to allow selected units to be kept out of the dynamic brake mode, it has been found that the switches are not always used properly by railroad personnel. As a result, it is not uncommon on consists with a large number of locomotives for the dynamic brake loading to be applied to more than the allowed number of axles, thus creating instability and the possibility of derailment. The present invention eliminates this problem by providing switches which can be preset by authorized personnel to select the number of locomotives available for dynamic braking. Like the minimum and maximum switches, the switches used for selection of dynamic brake availability are inaccessible to crewmen. Automatic bypassing of units having a problem in the dynamic brake circuit is also provided so that such units are not selected as being available for dynamic braking.